CN106711745A - Wide-tuning and narrow-linewidth nanosecond pulse double-resonance medium-infrared parameter oscillator - Google Patents

Abstract

A double-resonance, wide-tuning, narrow-linewidth all-solid-state nanosecond pulse mid-infrared optical parametric oscillator, which includes four parts: single-frequency pump light, double-resonance resonator, electrical control part and seed light. Frequency pulse laser pumps quasi-phase-matched multi-period polarized crystal dual-resonance parametric oscillator to obtain dual-band laser output with wide tuning range near-infrared signal light and mid-infrared idle light; the output center wavelength can be tuned in a wide spectral range, combined with The single-frequency continuous semiconductor laser seed injection technology dynamically adjusts the cavity length through the electro-optic crystal to realize the narrow linewidth laser output of the optical parametric oscillator. The invention can be widely used in the fields of high-resolution laser spectroscopy, laser radar, laser remote sensing, environmental detection, photoelectric countermeasures, laser medical treatment and the like.

Description

Wide-tuned, narrow-linewidth nanosecond-pulse dual-resonance mid-infrared parametric oscillator

technical field

The invention relates to an optical device, in particular to a nanosecond pulse double-resonance mid-infrared optical parameter oscillator with wide tuning and narrow line width. Wide tuning range laser output is realized through temperature, period and angle tuning, dual-band oscillation is realized through double-resonant ring cavity, and narrow linewidth laser output is realized by combining seed injection technology. It is suitable for laser spectroscopy, laser radar, laser remote sensing, environmental pollution detection, photoelectric detection, laser medical treatment and other fields.

Background technique

The near-infrared and mid-infrared are very important atmospheric windows in the optical band. The near-infrared band is not only the safest band for lasers to human eyes, but also lies in the atmospheric transmission window, which has a strong ability to penetrate smoke, so that high-precision wind measurement, radar, etc. can be developed for weather forecasting and global climate detection; The infrared band has a high transmittance to the atmosphere, and is less affected by the absorption of gas molecules and the scattering of suspended matter, and many polluting gases (SO ₂ , CO ₂ , NO ₂ , NH ₄ , NH ₃ , etc.) have strong absorption in the mid-infrared band Therefore, this band has important applications in laser ranging, laser radar, laser remote sensing, and high-sensitivity gas detection.

Optical parametric oscillators are currently the most common method for generating mid-infrared lasers. However, considering the damage threshold of crystals and films, traditional optical parametric oscillators usually have reflection linewidths of several nanometers, continuous working mode, and poor signal-to-noise ratio. The sensitivity is poor, and it is difficult to meet the needs of spectroscopy, laser remote sensing, environmental detection and other fields that require relatively high line width.

The dual-resonant oscillator satisfies the oscillation of signal light and idle light at the same time, and can realize laser output with a wide tuning range of 12 μm from ultraviolet to far infrared, and is not limited by the pumping wavelength.

Quasi-phase matching technology can maximize the use of the nonlinear coefficient of the crystal, adopt multiple ways of tuning, low threshold of oscillation, no walk-off effect, compact structure, and can achieve room temperature operation. Matching in the selected direction can make the energy continuous Convert from fundamental frequency light to parametric light.

Periodically polarized crystals doped with magnesium oxide (MgO:PPLN, MgO:PPLT) are high-efficiency wavelength conversion nonlinear crystals with wide light transmission range (0.4-4.5μm), long service life, effective nonlinear With the characteristics of high coefficient, low threshold and high efficiency, it is an important material for producing near-infrared-mid-infrared laser bands. Compared with MgO:PPLN, MgO:PPLT has a higher thermal conductivity. By tuning the temperature, period, and angle of the multi-period polarized crystal, a wide-tuned dual-wavelength output can be realized.

Conventional seed injection laser systems use piezoelectric ceramics to control the cavity length of the laser, but due to the nonlinear characteristics and oscillation of piezoelectric ceramics, the output single-frequency characteristics of the laser often deteriorate.

Contents of the invention

The purpose of the present invention is to provide a miniaturized, wide-tunable, and narrow-linewidth all-solid-state nanosecond pulse mid-infrared optical parametric oscillator, which solves key technical problems such as linewidth narrowing, frequency tuning, and spectrum control of the pulsed optical parametric oscillator. Any resonant single-frequency seed light can be injected to realize dual-band spectral narrowing of near-infrared signal light and mid-infrared idle light, and has a bright application prospect.

Technical solution of the present invention is as follows:

A wide-tuning, narrow-linewidth nanosecond pulse double-resonance mid-infrared parametric oscillator, characterized in that the oscillator includes four parts: single-frequency pump light, double-resonance resonator, electrical control part and seed light;

The pump optical path includes a 1.064 μm pump source, a focusing lens, a 1.064 μm half-wave plate and a polarizer mounted on a rotatable bracket;

The double-resonance resonator includes a plano-concave first cavity mirror, a multi-period polarized crystal fixed on a crystal temperature-controlled furnace, a plano-concave second cavity mirror, a planar third cavity mirror, a planar fourth cavity mirror and a beam splitter , the multi-period polarized crystal is fixed on the four-dimensional adjustment frame together with the crystal temperature control furnace, and is used to adjust the period and angle of the multi-period polarized crystal; it is inserted in the middle of the plane third cavity mirror and the plane fourth cavity mirror An electro-optic crystal, with a photodiode on the extension line of the two;

The electrical control processing part includes a photodiode, an electro-optic crystal, an electro-optic crystal drive source, an electro-optic modulator and a PID control system. The output end of the electro-optic crystal driving source is connected to the input end of the electro-optic crystal, the input end of the PID control system is respectively connected to the output end of the photodiode output end and the electro-optic modulator, and the PID control system The output end of the system is connected with the input end of the electro-optic crystal driving source.

Described seed light comprises single-frequency FPB seed laser, collimating lens, isolator, half-wave plate, focusing lens and semi-transparent mirror, and described collimating lens, half-wave plate and focusing lens are all coated with pair seed An electro-optic modulator is arranged on the transmission light path of the half-transparent half-mirror through a dielectric film with high light transmittance.

The propagation path along the pump light path is: the pump light emitted by the 1.064μm pump source is coupled and focused by the focusing lens, then passes through the 1.064μm half-wave plate, polarizer and dichroic mirror in turn, and then transmits from the plano-concave first cavity mirror. Incident to the center of the multi-periodically polarized crystal, the position and angle of the multi-periodically polarized crystal are adjusted through a four-dimensional adjustment frame to generate near-infrared signal light and mid-infrared idle light, and the remaining pump light is transmitted from the plano-concave second cavity mirror . The polarizer and the pump light path are placed at a Brewster angle, and the polarizer and the 1.064 μm half-wave plate constitute a light intensity adjustment device for adjusting the light intensity of the incident pump light;

The propagation path along the seed optical path is: the seed laser emitted by the single-frequency FPB seed laser passes through the collimating lens, isolator, half-wave plate, focusing lens, half-transparent mirror and dichroic mirror, and then is coupled to the pumping optical path, and then passes through the The plano-concave first cavity mirror is incident on the plano-concave second cavity mirror at an incident angle of 15° after passing through the multi-period polarized crystal, and then passes through the plano-concave second cavity mirror, the planar third cavity mirror, and the planar fourth cavity mirror in sequence The total reflection of the mirror is reflected back to the plano-concave first cavity mirror. After reflection, part of the seed laser incident on the plano-concave first cavity mirror is directly output through the plano-concave first cavity mirror and the beam splitter, and the other part is directly output through the plano-concave first cavity mirror and the beam splitter. The cavity mirror reflects back to the incident seed light path, forming an oscillating closed loop in the ring cavity. The focusing lens is used to couple the seed light to the central position of the multi-period polarized crystal. The dichroic mirror is coated with a dielectric film that is highly transparent to 1.064 μm and highly reflective at 45° for the seed light. The beam splitter is coated with There is a dielectric film that is highly transparent to near-infrared signal light and highly reflective to mid-infrared idle light.

In the working cycle of the electrical control part, the electro-optical modulator performs frequency and amplitude modulation on the seed light passing through the half-mirror, and the photodiode receives the interference formed by the transmission of the near-infrared signal light through the plane third cavity mirror. The signal is mixed with the signal after the electro-optic modulator to generate an error signal. The error signal is processed by the PID control system. The output of the PID control system drives the electro-optic crystal drive source. By adjusting the voltage of the electro-optic crystal drive source, the electro-optic crystal is driven to adjust the cavity length. , so that the signal light frequency of the optical parametric oscillator is locked on the seed laser frequency, and a narrow linewidth laser output is obtained. The electro-optic crystal is a gallium arsenide crystal, and the photodiode is an indium gallium arsenide photodetector.

The isolation degree of the isolator to the seed laser is not less than 20dB, which is convenient for effective protection of the seed laser.

The temperature control range of the crystal temperature control furnace is 20-200°C, and the temperature control accuracy is ±0.1°C.

The present invention has the following advantages:

1. Based on the 1.064μm laser-pumped multi-period polarized crystal output by a single-frequency pulse laser, through period, angle, and temperature tuning, tunable dual-resonance near-infrared-mid-infrared laser output can be obtained, with convenient tuning and wide coverage The advantages;

2. The ring cavity structure of the present invention is beneficial to stable oscillation of the laser mode and seed laser injection, and the double resonator can realize dual-resonance single-frequency parametric laser output of near-infrared signal light and mid-infrared idle light.

3. The present invention adopts active-passive combination frequency control technology to control the frequency characteristics of the semiconductor seed laser, and then injects it into the optical resonant cavity. Through the electro-optic crystal, the resonant cavity of the optical parametric oscillator is locked on the frequency of the seed laser to realize narrowing optical The line width of parametric light improves the efficiency of optical parametric conversion.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of a wide-tuning, narrow-linewidth nanosecond pulse double-resonance mid-infrared laser oscillator of the present invention.

Figure 2 is a wiring diagram for electrical control processing.

detailed description

In order to further illustrate the specific technical content of the present invention, below in conjunction with embodiment and accompanying drawing, describe in detail as follows:

Referring to Fig. 1 first, Fig. 1 is a structural schematic diagram of a wide-tuning, narrow-linewidth nanosecond pulse double-resonance mid-infrared parametric oscillator of the present invention. The present invention includes four parts: single-frequency pump light, double-resonance resonator, and electrical control part and seed light:

The single-frequency pump light includes a 1.064 μm pump source 1-1, a focusing lens 1-2, a 1.064 μm half-wave plate 1-3 installed on a rotatable bracket, a polarizer 1-4 and a dichroic mirror 1 -5;

The double-resonance resonator includes a flat-concave first cavity mirror 2-1, a multi-period polarized crystal 2-2 fixed on a crystal temperature control furnace 2-3, a flat-concave second cavity mirror 2-4, and a planar second cavity mirror 2-4. Three-cavity mirror 2-5, plane fourth cavity mirror 2-6 and beam splitter 2-7, described multi-period polarized crystal 2-2 is fixed on the four-dimensional adjustment frame together with crystal temperature control furnace 2-3, with To adjust the period and angle of the multi-period polarized crystal 2-2; the electro-optic crystal 3-2 is inserted in the middle of the plane third cavity mirror 2-5 and the plane fourth cavity mirror 2-6, and the extension line of the two is provided with photodiode 3-1;

Described seed light comprises single-frequency FPB seed laser 4-1, collimating lens 4-2, isolator 4-3, half-wave plate 4-4, focusing lens 4-5 and half mirror 4-6, An electro-optic modulator 3-4 is arranged on the transmitted light path of the half-mirror 4-6.

The propagation path along the pump light path is: the pump light emitted by the 1.064μm pump source 1-1 is coupled and focused by the focusing lens 1-2, and then passes through the 1.064μm half-wave plate 1-3, the polarizer 1-4 and the dichroic mirror After 1-5, it is transmitted from the plano-concave first cavity mirror 2-1, incident to the center position of the multi-period polarized crystal 2-2, and the position and angle of the multi-period polarized crystal are adjusted through the four-dimensional adjustment frame to generate near-infrared The signal light and mid-infrared idle light, and the remaining pump light are transmitted from the plano-concave second cavity mirror 2-3. The polarizer 1-4 and the pump light path are placed at a Brewster angle, and the polarizer 1-4 and the 1.064 μm half-wave plate 1-3 constitute a light intensity adjustment device for adjusting the incident pump light light intensity;

The propagation path along the seed optical path is: the seed laser emitted by the single-frequency FPB seed laser 4-1 passes through the collimator lens 4-2, isolator 4-3, half-wave plate 4-4, focusing lens 4-5, semi-transparent The mirror 4-6 and the dichroic mirror 1-5 are coupled to the pump light path, and then pass through the plano-concave first cavity mirror 2-1, and then pass through the multi-period polarized crystal 2-2 and enter the The plano-concave second cavity mirror 2-4 is then reflected back to the plano-concave first cavity mirror through the total reflection of the plano-concave second cavity mirror 2-4, the plane third cavity mirror 2-5, and the plano-concave fourth cavity mirror 2-6. Cavity mirror 2-1, after reflection, part of the seed laser incident on the plano-concave first cavity mirror 2-1 is directly output through the plano-concave first cavity mirror 2-1 and the beam splitter 2-7, and the other part passes through the plano-concave first cavity mirror 2-1 and the beam splitter 2-7. A cavity mirror 2-1 reflects back to the incident seed light path, forming an oscillating closed loop in the annular cavity. The focusing lens 4-5 is used to couple the seed light to the central position of the multi-period polarized crystal 2-2, and the dichroic mirror 1-5 is coated with 1.064 μm high transparency and 45° high reflection of the seed light Dielectric film, the beam splitter 2-7 is coated with a dielectric film that is highly transparent to near-infrared signal light and highly reflective to mid-infrared idle light.

In the working cycle of the electrical control part, the electro-optic modulator 3-4 performs frequency and amplitude modulation on the seed light passing through the half-mirror 4-6, and the photodiode 3-1 receives the near-infrared signal light passing through The interference signal formed by the transmission of the plane third cavity mirror 2-5 is mixed with the seed optical signal passed through the electro-optic modulator 3-4 to generate an error signal, and the error signal is processed by the PID control system 3-4, and the PID control system 3 The output of -4 acts on the electro-optic crystal drive source 3-3, and the electro-optic crystal 3-2 is driven by adjusting the voltage of the electro-optic crystal drive source, and the length of the cavity is adjusted, so that the optical frequency of the near-infrared signal of the optical parametric oscillator is locked on the seed laser frequency, Obtain narrow linewidth near-infrared signal light and mid-infrared idle light output. The electro-optic crystal 3-2 is a gallium arsenide crystal, and the photodiode 3-1 is an indium gallium arsenide photodetector.

The 1.064 μm pump source 1-1 is a Nd:YAG Q-switched laser pumped by a laser diode, the output wavelength is 1.064 μm, and the linewidth is close to the Fourier transform limit.

The plano-concave first cavity mirror 2-1 is coated with a dielectric film that is anti-reflective to 1.064 μm, partially transmits near-infrared signal light and mid-infrared idle light, and has the same transmittance; The second cavity mirror 2-4 is coated with a dielectric film that is antireflective to 1.064 μm and highly reflective to both near-infrared signal light and mid-infrared idle light. 1.064μm high transmittance, high transmittance for near-infrared signal light, high reflective dielectric film for mid-infrared idle light, the other side is coated with 1.064μm high transmittance, high reflective film for mid-infrared idle light; the fourth plane The cavity mirror 2-6 is coated with a dielectric film with high transparency of 1.064μm, high reflection of near-infrared signal light and mid-infrared idle light.

The material of the multi-period poled crystal 2-2 is MgO:PPLN or MgO:PPLT, and its polarization structure is a multi-period structure, and the polarization period is 29 μm, 29.5 μm, 30 μm, 30.5 μm, and the interval changes, The size is 50mm*3mm*7mm. Both ends of the multi-period polarized crystal are coated with a dielectric film that is anti-reflection for 1.064μm, near-infrared and mid-infrared bands. For the convenience of tuning, the multi-period polarized crystal and the crystal temperature control furnace are fixed together on a four-dimensional adjustment frame, which is convenient for period, angle and temperature tuning of the crystal.

The single-frequency FPB seed laser 4-1 is a single-frequency semiconductor seed laser locked by a high-precision temperature and high-precision current frequency stabilization scheme.

The temperature control range of the crystal temperature control furnace 2-3 is 20-200°C, and the temperature control accuracy is ±0.1°C.

The collimating lens 4-2 and the focusing lens 4-5 change the beam of the seed laser so that the spot size of the parametric resonant light in the ring resonator is consistent with that of the parametric resonant light to achieve the best mode matching.

The isolator 4-3 can ensure the one-way transmission of the seed laser, avoiding the surface reflection of the optical device or the laser leaking from the rear cavity mirror entering the seed laser and damaging the seed laser. The isolation degree of the isolator to the seed laser is not less than 20dB .

The working process of the specific embodiment of the present invention is that the 1.064 μm non-polarized laser light output by the Nd:YAG pump laser 1-1 passes through the focusing lens 1-2, and its focus is focused on the center of the multi-period polarized crystal 2-2, coupled The diameter of the pump spot to the multi-period polarized crystal 2-2 is 800 μm; and then through the light intensity adjustment device composed of the half-wave plate 1-3 and the polarizer 1-4, the pump light intensity incident on the ring resonator is adjusted The single-frequency laser light produced by the single-frequency FPB seed laser 4-1 is collimated into a parallel beam by the collimating lens 4-2, passes through the isolator 4-3, and then is focused to the multi-period polarized crystal 2 by the focusing lens 4-5 At the center of -2, the diameter of the seed spot coupled to the multi-period polarized crystal is 600 μm, and then coincides with the pump light path through the dichroic mirror 1-5, and is incident into the double-resonant ring cavity. The 1.064μm pump light undergoes frequency conversion and oscillation inside the multi-period polarized crystal 2-2. (3.0～4.5μm) is emitted from the plano-concave first cavity mirror 2-1 along the direction of 30° to the incident pump light, and the remaining pump light is emitted from the plano-concave second cavity mirror 2-4; the output mid-infrared is idle Light and near-infrared signal light are separated by the beam splitter 2-7, the signal light is coupled into the wavelength meter through the optical fiber, and the specific resonance wavelength of the output signal light is measured, and the current and temperature parameters of the single-frequency DFB seed laser 4-1 are adjusted. Control so that the output wavelength center is consistent with the center wavelength of the measured signal light output. Part of the single-frequency FPB seed laser 4-1 is injected into the double-resonance ring cavity, and part of it is tuned by the electro-optic modulator 3-4 for frequency and amplitude. The photodiode 3-2 is used to detect the signal light signal transmitted through the plane third cavity mirror , and converted into an electrical signal, the electrical signal is band-pass filtered, amplified, and mixed with the electro-optical modulated signal to form an error signal, and then the error signal is processed by the PID controller system 3-5, and the output of the PID control system Drive the electro-optic crystal drive source 3-3, the electro-optic crystal drive source applies voltage to the piezoelectric crystal 3-2, the refractive index of the electro-optic crystal changes linearly, and then quickly adjusts the cavity length, so that the optical frequency of the output signal is always locked at the seed laser frequency , so as to output narrow-linewidth near-infrared signal light and mid-infrared idle light.

Experiments show. The invention realizes signal light (1.3-1.7 μm) and idle light (3.0-4.5 μm) width by pumping ring-shaped dual-resonance resonator with single-frequency 1.064 μm laser, combined with multi-period polarization crystal cycle, angle, and temperature tuning. Tuning range laser output; by injecting a seed laser with the same frequency as the signal light, the output of single-frequency mid-infrared idle light and near-infrared signal light can be realized, which effectively narrows the line width and makes the output laser spectral width less than 0.1nm, overcoming The technical problems of the traditional optical parametric oscillator, such as the transmission line width of several nanometers, continuous working mode, poor signal-to-noise ratio, and poor detection sensitivity, have been overcome. The invention has the characteristics of wide tuning, double resonance and good single frequency performance.

Claims (6)

1. A wide-tuning, narrow-linewidth nanosecond pulse double-resonance mid-infrared parametric oscillator, characterized in that the oscillator includes: four parts: single-frequency pump light, double-resonance resonator, electrical control part and seed light; The single-frequency pump light includes a 1.064 μm pump source (1-1), a focusing lens (1-2), a 1.064 μm half-wave plate (1-3) installed on a rotatable support, a polarizer ( 1-4) and dichroic mirrors (1-5); The double-resonance resonator includes a flat-concave first cavity mirror (2-1), a multi-period polarized crystal (2-2) fixed on a crystal temperature-controlled furnace (2-3), a flat-concave second cavity mirror (2-4), the third cavity mirror of the plane (2-5), the fourth cavity mirror of the plane (2-6) and the beam splitter (2-7), the described multi-period polarized crystal (2-2) and The crystal temperature control furnace (2-3) is fixed together on the four-dimensional adjustment frame for adjusting the period and angle of the multi-period polarized crystal (2-2); the third cavity mirror (2-5) on the plane and the fourth cavity mirror on the plane An electro-optic crystal (3-2) is inserted in the middle of the cavity mirror (2-6), and a photodiode (3-1) is arranged on the extension line of the two; The electrical control processing part includes a photodiode (3-1), an electro-optic crystal (3-2), an electro-optic crystal driving source (3-3), an electro-optic modulator (3-4) and a PID control system (3-5 ), the output end of the electro-optic crystal driving source (3-3) is connected with the input end of the electro-optic crystal (3-2), and the input end of the described PID control system (3-5) is respectively connected with the photoelectric The output end of the diode (3-1) is connected to the output end of the electro-optical modulator (3-4), and the output end of the PID control system (3-5) is connected to the output end of the electro-optic crystal drive source (3-3). connected to the input; Described seed light comprises single-frequency FPB seed laser (4-1), collimator lens (4-2) placed successively along the seed laser direction that this single-frequency FPB seed laser (4-1) sends, isolator (4 -3), half-wave plate (4-4), focusing lens (4-5) and half-mirror (4-6), described electro-optic modulator (3-4) is arranged on half-mirror (4-6) on the transmitted light path; The propagation path along the pump light path is: the pump light emitted by the 1.064μm pump source (1-1) is coupled and focused by the focusing lens (1-2), and then passes through the 1.064μm half-wave plate (1-3) and the polarizer in turn After (1-4), it is incident on the dichroic mirror (1-5), and after the transmitted light of the dichroic mirror (1-5) is transmitted from the plano-concave first cavity mirror (2-1), it is incident on the multi-period polarization The center position of the crystal (2-2), adjust the position and angle of the multi-period polarized crystal (2-2) through a four-dimensional adjustment frame to generate near-infrared signal light and mid-infrared idle light, and the remaining pump light is from the flat concave second The cavity mirror (2-4) is transmitted; the polarizer (1-4) and the pump light path are placed at a Brewster angle, and the polarizer (1-4) and the 1.064 μm half-wave plate (1 -3) constituting a light intensity adjustment device for adjusting the light intensity of the incident pump light; The propagation path along the seed optical path is: the seed laser emitted by the single-frequency FPB seed laser (4-1) passes through the collimator lens (4-2), the isolator (4-3), the half-wave plate (4-4) and the focusing After the lens (4-5), it is incident on the half-mirror (4-6), and after being reflected by the half-mirror (4-6), it is reflected in the dichroic mirror (1-5), and passes through the dichroic mirror (1 -5) Coupled to the pumping optical path, passing through the first plano-concave cavity mirror (2-1), and then entering the plano-concave second cavity mirror at an incident angle of 15° after passing through the multi-period polarized crystal (2-2) After (2-4), it is reflected back to the plano-concave first cavity through the total reflection of the plano-concave second cavity mirror (2-4), the planar third cavity mirror (2-5), and the planar fourth cavity mirror (2-6). A cavity mirror (2-1), part of the seed laser is directly output through the plano-concave first cavity mirror (2-1) and the beam splitter (2-7), and the other part passes through the plano-concave first cavity mirror (2-7) again -1) reflection to the multi-period polarized crystal (2-2), forming an oscillating closed loop in the annular cavity; the focusing lens (4-5) is used to couple the seed light to the multi-period polarized crystal (2-2 ), the dichroic mirror (1-5) is coated with a dielectric film that is highly transparent to 1.064 μm and 45° highly reflective to the seed light, and the beam splitter (2-7) is coated with a dielectric film that is highly reflective to near-infrared signal light Highly transparent, highly reflective dielectric film for mid-infrared idle light; In the working cycle, the electro-optic modulator (3-4) performs frequency and amplitude modulation on the seed light passing through the half-mirror (4-6), and the photodiode (3-1) receives the near-infrared signal light through The interference signal formed by the transmission of the plane third cavity mirror (2-5) is mixed with the signal passed through the electro-optic modulator (3-4) to generate an error signal, and the PID control system (3-5) receives the error signal and performs Circuit processing, the output of the PID control system (3-5) drives the electro-optic crystal drive source (3-3), drives the electro-optic crystal (3-2) by changing the voltage of the electro-optic crystal drive source (3-3), and dynamically adjusts the cavity in real time Long, the near-infrared signal light frequency of the optical parametric oscillator is locked on the seed laser frequency, and the output of narrow-linewidth near-infrared signal light and mid-infrared idle light is obtained. 2. wide tuning as claimed in claim 1, narrow line width nanosecond pulse double resonance mid-infrared parametric oscillator, it is characterized in that described 1.064 μm pumping source (1-1) is the single-frequency laser of pulse operation, The output wavelength is 1.064 μm, the output pump light is unpolarized light, and the line width is close to the Fourier transform limit. 3. wide tuning as claimed in claim 1, narrow line width nanosecond pulse double resonance mid-infrared parametric oscillator, it is characterized in that described plano-concave first cavity mirror (2-1) is coated with to 1.064 μ m anti-reflection , a dielectric film that partially transmits near-infrared signal light and mid-infrared idle light and has the same transmittance; the flat-concave second cavity mirror (2-4) is coated with anti-reflection for 1.064 μm, and for near-infrared Highly reflective dielectric film for both signal light and mid-infrared idle light. The plane third cavity mirror (2-5) is coated with a reflective surface in the cavity that is highly transparent to 1.064 μm and highly transparent to near-infrared signal light. A dielectric film with high reflection for infrared idle light, the other side is coated with a high-transparency film for 1.064 μm and a high-reflection film for mid-infrared idle light; Dielectric film with high reflection for both near-infrared signal light and mid-infrared idle light. 4. wide tuning as claimed in claim 1, narrow line width nanosecond pulse double resonant mid-infrared parametric oscillator, it is characterized in that described single-frequency FPB seed laser (4-1) is by high precision temperature and high precision A single-frequency semiconductor seed laser locked by a current frequency stabilization scheme. 5. wide tuning as claimed in claim 1, narrow line width nanosecond pulse double resonance mid-infrared parametric oscillator, is characterized in that, the polarization structure of described multi-period polarized crystal (2-2) is multi-period structure, the polarization period is 29μm, 29.5μm, 30μm, 30.5μm, and the polarization period changes at equal intervals. The dielectric film of the multi-period poled crystal is MgO:PPLN or MgO:PPLT. 6. wide tuning as claimed in claim 1, narrow line width nanosecond pulse double resonance mid-infrared parametric oscillator, it is characterized in that the wavelength tuning mode of near-infrared signal light and mid-infrared idle light is by changing the multi-period polarized crystal (2-2) The temperature, translational temperature control multi-period poled crystal, and adjusting the angle of the multi-period polarized crystal realize temperature, period and angle tuning.